a) Field of the Invention
The present invention relates to a caller ID system, and more particularly to a caller ID system wherein an enterprise which uses a conventional telephone switch can apply a network transmission technique, with its own computers and network, to construct a multimedia caller ID system that can correctly send caller information to a computer corresponding to the dialed extension, without changing the internal structure of original switch or switchboard.
b) Description of the Prior Art
For the related techniques and methods used for improving a conventional switch to a caller ID system, the internal structure of software and hardware of the switch should be changed, along with the replacement of the hardware of original telephone extension, such as the installation of a telephone card with caller ID at a trunk-line side and a house-line side. Moreover, the caller ID cannot be transmitted to an extension phone without the modification of internal software programs of the switch. On the other hand, all the extension devices intending to display the caller ID should be replaced with telephones with displaying screen. Therefore, it incurs higher cost, and is usually hard to accept for an enterprise with a conventional telephone switch. Telecommunication systems that simply use network to send news briefs or other multimedia messages cannot be combined with the function of extension forwarding. Other fax servers that use the function of extension forwarding to categorize faxing documents cannot send caller information to a specified network client-side program at that extension.
Patents regarding prior art telephone switch of caller ID techniques are listed below:                (1) Taiwan Patent No. 049470 (Mar. 16, 1983)        (2) Taiwan Patent No. 059276 (Jun. 16, 1984)        (3) Taiwan Patent No. 374277 (Nov. 11, 1999)        (4) Taiwan Patent No. 384595 (Mar. 11, 2000)        (5) Taiwan Patent No. 411689 (Nov. 11, 2000)        (6) Taiwan Patent No. 474089 (Jan. 21, 2002)        (7) Taiwan Patent No. 544590 (Aug. 1, 2003)        (8) Taiwan Patent No. 548944 (Aug. 21, 2003)        (9) Taiwan Patent No. 548945 (Aug. 21, 2003)        